The present invention relates to a hermetically sealed electrical connector. More specifically, the connector is used to pass electrical signals from the interior to the exterior of a hermetically sealed container. A process is disclosed to achieve a robust, hermetically sealed connector.
In certain environments, it is necessary to isolate electrical equipment from the outside world. In many applications this is accomplished by placing the necessary elements within some type of canister or container, and then hermetically sealing the container to avoid any environmental contamination such as humidity and undesired gases.
When using hermetically sealed canisters, it is typically necessary to pass electrical signals from the exterior of these canisters to the interior. These electrical signals may be power supplies, control signals, or readout signals. In order to maintain the integrity of the hermetic seal around such a canister, it is necessary that the connectors, or devices for passing electrical signals from the exterior to the interior, maintain the integrity of the hermetic seal.
Many materials can be used to fabricate the necessary connectors, such as metals, machineable plastics, or moldable plastics. An example of a machineable, or moldable, plastic used for fabricating connectors is Ryton.RTM..
The problem with many machined plastic connectors is their inability to maintain the integrity of their hermetic seal. For example, many connectors begin to leak after they have been temperature-cycled for a period of time. Once the seal begins to leak, many problems are created since this destroys the entire reason for hermetically sealing a container.
Many of the aforementioned leaks result from inadequate sealing techniques. The use of incorrect sealants, or potting materials, results in unnecessary stresses in the connector due to filler settling. Filler material placed in the sealant results in a coefficient of thermal expansion (CTE) differential within the cured sealant itself. If the filler material settles in the sealant (the filler migrates to one area within sealant), the CTE differential creates a much larger problem due to the possibility of increased thermal expansion. This CTE differential, in conjunction with any inherent CTE differential within the plastic connector, causes stresses during thermal cycling resulting in leaks. Furthermore, high shear stress occurs in the sealant-connector housing interface as the connector is exposed to high and low temperatures. This high shear stress causes the hermetic seal to leak.